Itaricans

Hi all, I have a T B Pony and this am I started mowing when the belt came off, I went in the garage and put it back on, but when I started the engine, the belt started smoking. I shut down the engine, and then tried to run it again but the whole cutting deck shakes when I turn the key, also the the engine tries to turn over without me on the seat, which tells me a safety switch somewhere is bad, but I don`t know which one. Does anyone has any ideas as to what`s wrong? Thanks for any help. Latter. Louie.